Pulverizer



1955 N. w. EFT ETAL 3,199,797

PULVERIZER Filed May 25. 1962 2 94 'qro 23 I 6 [I ll; 4 E (1 l 45 1o h 3 6O 4 z 63 I I I 57 E 5 *14 I In 1- E 43 I I 1 so 53 n 7$ 6 q I; 37 I36 U I 4o 8 INVENTORS Neil W. Eff BY Richard A. Miller ATTORNEY United States Patent 3,199,797 PULVERTZER Neil W. lift and Riehm'd A. h'fiiier, Alliance, Ohio, assignors to The Eahcoclr Wilcox Company, New York, N.Y., a corporation of New Jersey Filed May 23, 1962, Ser. No. 197,962 5 Claims. (Cl. 241117) This invention relates in general to improvements in the construction and operation of pulverizers, and more particularly to pulverizers in which a circular series of rolling grinding elements are positioned between relatively moving upper and lower grinding rings. The rings of the pulverizer are urged together to exert a pressure on the contacting surfaces of the rings and balls so that raw materials introduced generally into the grinding zone formed by the rings and balls will be pulverized in passing outwardly therethrough for discharge from the outer periphery of the zone. Certain features of the pulverizer disclosed in this application are disclosed and claimed in copending applications of Edward M. Boole, Serial No. 197,061 filed May 23, 1962; and of James L. Harvey and Alden Q. Beaty, Serial No. 198,682, filed May 29, 1962, now Patent 3,093,327 issued July 29, 1963 In the present invention a pulverizer of the ring and ball type is provided wherein the upper and lower rings are rotated in opposite directions to increase the effective grinding area utilized in pulverization. The increased grinding area increases the capacity of the pulverizer without a corresponding increase in its size, and without increasing the centrifugal forces imposed on the rolling grinding elements operating between the rotating upper and lower rings. In a preferred form of the invention the rings are separately driven from separate motors. While the lower ring is driven through suitable gearing from its drive motor, the upper ring is rotated through a plurality of single turn coil springs interposed between the ring and the drive mechanism. The single turn coil springs not only provide a structural connection between the drive mechanism and the upper grinding ring, but also provide for the imposition of a resilient downward pressure on the grinding elements. The rates of rotation of the upper and lower rings are different so that the circular row of rolling grinding elements will rotate a a slow speed about the central axis of the ring drive shafts. The centrifugal forces imposed on such elements will be low while the effective grinding surface is high relative to the floor area occupied by the pulverizer.

The invention is particularly useful in a pulverizer arranged for air-swept service, as in preparing solid fuels, such as bituminous coal, for suspension burning. In such an arrangement, carrier air is passed upwardly in an annular stream around the periphery of the pulverizing elements or zone to entrain the discharged wholly and partially pulverized solids, which are thereafter classified in the upper portion of the pulverizer. The classification stage separates the desired finished product, for air-borne removal from the pulverizer, from the oversized materials which are returned to the grinding elements for further pulverization.

The various features of novelty which characterize our invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which we have illustrated and described a preferred embodiment of the invention.

The single figure of the drawings is an elevation, in section, of a pulverizer constructed and arranged in accordance with the present invention.

In general, the pulverizer illustrated includes a cylin- Faterited Aug. 19, 1%55 "ice drical upper housing section 10 and a lower housing section 11 supported on a foundation 12. The sections 16 and 11 are fastened together for ease of assembly, and the section 1 may be made in two cylindrical portions 13 and 14- for ease of access to the grinding and classification zones hereinafter described. The lower housing sec tion 11 encloses a gear housing 15 which is separately supported by the foundation 12. As hereinafter described the gear housing 15 contains two worm-gear speed reducers each connected to its respective drive shaft, one of which drives the lower grinding ring while the other drives the upper grinding ring, both rings being positioned within the pulverizing or grinding zone 16. Each wormgear reducer is directly conected with a separated, externally positioned drive motor (not shown).

Raw coal supplied to a regulable feeder 17 discharges the coal into the grinding zone 15 through a chute 13 extending through the housing 19 from the feeder. Air, at superatmospheric pressure, enters the lower section 14 of the pulverizer housing 1% through an encircling duct 2%), to pass upwardly adjacent the outer side or periphery of the grinding zone 16, entraining comminuted coal, and thence through a classifier or separator 21, with the airborne finished product leaving the pulverizer housing section 13 through a centrally located upper outlet 22. The oversized material is passed downwardly from the classifier 21 into an annular discharge port 23 for return to the puverizin g zone 16. p

The grinding zone of the pulverizer includes a lower horizontally disposed grinding ring 24 having a circular groove or race 25 formed in its upper face to support a circular row of grinding balls 26. The balls in turn support an upper grinding ring 27 which is provided with a circular groove or race 28 in its lower face engaging the circular row of balls. In accordance with this invention both the upper and lower grinding rings 27 and 24, respectively, are rotated, but in opposite directions and at different rates of rotation. The rate of rotation of the row of balls about the axis of ring rotation will generally be equal to one-half the difference between the rates of ring rotation. This low ball row rotation rate results in a low value of centrifugal force imposed on the balls wh le maintaining a high rate of application of grinding force or work on the material being pulverized in any unit of time, leading to extremely high rates of pulverization per unit of floor space occupied by the pulverizer.

The lower grinding ring 24 is provided with a flat lower face supported on and pinned to the T shaped annular ledge member 3% and to the annular upper surface of a generally conical driving rotor 31, the shank 32 of the member 30 being interposed between the ring 24 and the rotor 31. The rotor 31 is affixed to the upper end portion of a stub shaft 33 which is rotated by a worm-gear drive assembly 34 positioned in the upper portion of the gear housing 15.

As shown in FIG. 1, the generally vertical arms of the member 30 extend above and below the shank 32. The upper arm 35 of the member 36 forms an upstanding ledge to restrict the flow of pulverized material from the grinding zone 16, while the outer surface of the arm 35 is shaped to cooperate with a stationary ring member 36 in defining a throat 37 for directing the upward flow of entraining air within the grinding zone. As shown, the cooperating surfaces defining the throat 37 direct the entraining air upwardly and slightly outwardly toward the housing section 14 of the pulverizer. Thus, the air passing through the duct 2% enters the pulverizer housing section 14 through a varied annular opening 38 discharging in an inward direction into a chamber 40 and thence upwardly through the throat. The chamber at is inwardly defined by the upper and lower arms 35 and 41, respectively of the rotating member 30, a lower fixed ring 42,

and at the top by the lower portion of member 36, and in part by the throat opening 37. The ring 36 is provided with a spring loaded displaceable section (not shown) which will be forced outwardly toward the housing by foreign materials such as tramp iron, or the like. Such foreign materials will fall by gravity into chamber 40 and discharge downwardly into box 39, from which the materials may be periodically removed.

In accordance with the invention the upper ring 27 is rotated and urged downwardly against the row of balls by a plurality of circumferentially equally spaced, single turn coil springs. In the embodiment shown, the springs 43 are attached to an annular member 44 which is supported by upright bolts 45, and a drive yoke 46 which is attached to the upper end portion of a shaft 47. The coil of each of the springs 43 is generally horizontally oriented and provided with oppositely extending upright end portions. The lower end extension 50 of each spring projects downwardly into a pocket or recess 51 formed in the upper outer portions of the ring 27 and is locked in place by a set screw 52. The opposite, or upper end extension 53 of each spring is fitted into a recess 54 formed in the lower portion of the member 44 and is locked in place by a set screw 55. Each of the recesses 51 and 54 are positioned in vertical alignment, and each spring 43 is arranged with its coil portion projecting inwardly and horizontally of the opposed end extensions 50 and 53 so as to leave clear the space between the member 44 and the housing for upward movement of air entrained solids therethrough.

The number 44 is provided with circumferentially equally spaced openings 56 therethrough each of which receives a sleeve 57 and the lower end portion of a vertically adjustable bolt 45. Each of the bolts 45 is threaded and projects upwardly through an opening 60 formed in an arm 61 of the yoke 46, and is locked in an adjustable position relative to the arm by lock nuts 62 and 63.

In the construction described, the springs 43 are rigidly fixed with respect to the member 44 which in turn is vertically positioned with respect to the yoke 46 so that the grinding pressure exerted on the pulverizing zone 16 is adjustable. The springs are used to transmit rotational movement to the upper ring 27 from the drive mechanism. Simultaneously they restrain lateral movement of the ring 27 during rotation and by reason of the flexibility of the springs permit a restrained tilting of the ring 27, as may be caused by the presence of foreign materials, such as tramp iron, in the pulverizing zone 16. The positional relationship of the member 44, bolts 45 and the yoke 'arms 61 is such as to minimize abrasion of the bolts 45 by the rising stream of pulverized material entrained in the air, which occurs particularly adjacent the housing 10, and minimizes the imposition of bending forces on 'the adjustable bolts 45. In effect the bolts can be considered fixed end beams due to their fixed relationship to the annular member 44 and the arms 61 of the yoke.

As shown in FIG. 1, the shafts 33 and 47 are coaxial, with the shaft 47 supported by thrust bearing 62 and radial bearing 63 engaging the gear housing 15. Immediately above the bearing 62 the shaft 47 is provided with a gear ring 64 which is bolted to a hub 65. The gear ring 64 engages a worm 66 driven by a motor (not shown) to transmit rotational movement to the shaft 47.

The shaft 33, driving the lower ring 24, is coaxial with and supported on the shaft 47 through combination thrust and radial bearing 70 and radial bearings '71 and 72. The radial bearing 71 maintains the axial relationship of the shaft 33 with respect to the gear housing while the radial bearing 72 maintains the coaxial relationship between shafts 47 and 33. The drive arrangement 34 includes a worm 73 driven by a motor (not shown) and drivingly engaging a worm-gear 74 affixed to the shaft 33.

The worm-gear drives and the bearings are suitably lubricated, and since the upper portions of both of the shafts extend into the housing 111 and are exposed to the material-laden air therein it is necessary to protect the bearing lubrication and bearing surfaces by a suitable air seal arrangement. Sealing air enters through a pipe 75 extending through the housing section 11 with a connecting duct 76 ending in an annular plenum chamber 79 adjacent the external surface of the rotating member 31. The member 31 is drilled to form air flow passageway 73 parallel to the axis thereof with the upper end opening into a rotating chamber 77 afiixed to the upper end of shaft 33, while the lower end of the passageways are each provided with an outwardly opening radial extension which is located at the level of the chamber 79. With the construction described, sealing air is introduced into the pipe 75 at a pressure in excess of the pressure prevailing within the pulverizer and passes from chamber 79 upwardly through the passageway 78 into the chamber 77. Any sealing air which escapes from the plenum chamber 79 between the rotating and stationary parts thereof discharges either downwardly and into the atmosphere or upwardly into the pulverizer housing beneath the member 31. The latter portion of escaping seal air eventually passes between hte outer end of the arm 41 and the inner end of the part 42, and thus mingles with the carrier air passing through the chamber 40.

Since the chamber 77 rotates with the shaft 33 a running clearance is formed between the upper and lower walls 81 and 82, respectively, of the chamber so that some of the sealing air will escape in the space between the shaft 47 and the upper wall 81 into the interior of the pulverizer housing 16. The outward flow of such sealing air will prevent infiltration of dust-laden air into the bearings of the pulverizer drive shafts. The remained of the sealing air delivered to the chamber 77 will discharge downwardly along the shaft 47, between the shaft and the end of the wall 82,'into a chamber 83 and thence through one or more passageways 84 in member 31 into space 85 beneath a stationary diaphragm plate 86 which forms the lower wall of the pulverizer housing section 14. The space 85 defined by the diaphragm S6 and the top of the gear housing 15 is open to the atmosphere.

The mixture of pulverized material and air passing upwardly in an annular stream adjacent the inner wall of the housing sections 13 and 14 enters the classifier 21 through a series of circumferentially disposed angularly positioned upright vanes 90 located downwardly adjacent the upper plate 91 forming the top of the pulverizer housing. The vanes 90 are attached to the plate 91 and are provided with adjustable end portions 90A which may be extended or retracted to alter the fineness characteristics of the finished product. The lower edges of the vanes 90 are attached to the base flange of an inverted frusto-conical member 92 extending downwardly to the annular opening 23 for the discharge of separated coarser solid materials from the classifier 21. The opening 22 in the top of the pulverizer is provided with a depending duct 94 extending downwardly into the classifier and thereby providing an outlet for air-borne classified material to leave the pulverizer housing 10. The lower end of the duct 94 is provided with an adjustable cylindrical member 95 which embraces'the duct 94 and is vertically adjustable for a relatively minor regulation of the fineness limits of the materials discharged from the pulverizer.

As shown, the inner side of the lower annular classifier discharge opening 23 is defined by a cylindrical cap member 96 which is attached to the yoke 46 and I0- tates therewith. The cap member protects the upper end of the shaft 47, and the yoke 46 attachment to the shaft, and provides a support for a vaned rotor 97 operating in the opening 23 to reduce the back flow or leakage of air-borne materials upwardly through the opening. A similar seal construction is disclosed in U.S. Patent 2,762,573.

It will be noted all of the rotating parts, with the exception of the worm drives and their shafts, are arranged is in a. closed stress loop to minimize vibration and mechanical stress on the rotating parts. T he pressure Xerted on the rings and balls by the springs 43 is contained with in the coaxially arranged shafts 47 and 33, and the combined radial and thrust bearing 70. Thus the upward thrust of the member 44, as caused by the compression of the springs 43 and by operation of the grindin zone, is transmitted through the bolts 45 and arms 61 to the shaft 47, and results in an upward thrust against the hearing 79. At the same time the downward thrust on the ring 27 from the springs 43 is transmitted through the balls 28, ring 24 and yoke 31 to the shaft 33 results in a downward thrust against the bearing 7%. Generally speaking, the net downward thrust at the bearing 70 will be substantially equal to the dead weight or" the assembly of the rotating parts so that the lower thrust bearing 62 need only be sized to support the dead weight of the rotating parts.

In the embodiment of the invention, the pulverizer is rated for a grinding capacity of 50 tons per hour of a medium low grindability bituminous coal at a product fineness of 70% passing the 200 mesh US. Standard screen. To attain this capacity the pitch diameter of the grinding zone is 84 inches, the shaft 33 is rotated at 62 rpm. and shaft 47 is rotated at 82 r.p.m.

While in accordance with the provisions of the statutes we have illustrated and described herein the best form and mode of operation of the invention now known to us, those skilled in the art will understand that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by our claims, and that certain features of our invention may sometimes be used to advantage without a corresponding use of other features.

What is claimed is:

l. A pulverizer comprising a housing, a lower rotary grinding ring, means for rotating said lower grinding ring, a cicular row of rolling grinding elements supported on said lower grinding ring, a rotary upper grinding ring supported on said grinding elements, means for rotating said upper grinding ring in a direction opposite to the direction of rotation of said lower grinding ring including means for imposing a resilient grinding pressure on said grinding rings and elements, said resilient grinding pressure means simultaneously providing the sole driving connection between said rotating means and said upper grinding ring for rotating said upper ring, means for delivering material to be pulverized to said row of grinding elements, and means for withdrawing pulverized material from said housing.

2. A pulverizer comprising a housing enclosing a lower rotary grinding ring, means for rotating said lower grinding ring about a vertical axis, a circular row of rolling grinding elements supported on said lower grinding ring, a rotary upper grinding ring supported on said grinding elements, means for rotating said upper grinding ring about an axis common with the axis of and in a direction opposite to the direction of rotation of said lower grinding ring including a shaft having a yoke attached thereto and resilient means between said yoke and said upper ring and for imposing a grinding pressure on said grinding rings and elements, said resilient means providing the sole attachment between said yoke and upper grinding ring means for delivering material to be pulverized to said row of grinding elements, and means for Withdrawing pulverized material from said housing.

3. A pulverizer comprising a housing enclosing a lower rotary grinding ring, means for rotating said lower grinding ring, a circular row of rolling inding elements supported on said lower grinding ring, a rotary upper grinding ring supported on said grinding elements, means for rotating said upper grinding ring in a direction opposite to the direction of rotation of and at a greater rate than said lower grinding ring, means for imposing a resilient grinding pressure on said grinding rings and elements including circumferentially equally spaced single turn coil springs connected to said upper grinding ring and said means for rotating the upper grinding ring, means for delivering material to be pulverized to said row of grinding elements, and means for withdrawing pulverized material from said housing.

4. A pulverizer comprising a housing having a pulverized material outlet and a stationary classifier in the upper portion thereof, a lower rotary grinding ring, means for rotating said lower grinding ring, a circular row of rolling grinding elements supported on said lower grinding ring, a rotary upper grinding ring supported on said grinding elements, means for rotating said upper grinding ring about an axis common with the axis of and in a direction opposite to the direction of rotation of said lower grinding ring including single turn coil springs drivingly interconnecting said rotating means and said upper ring and imposing grinding ressure on said grinding rings and elements, means for delivering material to be pulverized to said row of grinding elements, and means for withdrawing pulverized material from said housing including a restricted annular air flow passageway between said housing and the periphery of said lower grinding ring, and means for passing a stream of carrier air upwardly though said annular passageway to entrain material passing outwardly through the grinding elements for movement to said classifier and for the discharge of the finer portion of said pulverized material through said outlet.

5. A pulverizer comprising a housing, a lower rotary grinding ring, means for rotating said lower grinding ing, a circular row of rolling grinding elements supported on said lower grinding ring, a rotary upper grinding ring supported on said grinding elements, means for rotating said upper grinding ring in a direction opposite to the direction of said lower grinding ring, spring means -for imposing a resilient downward grinding pressure on said upper grinding ring, said spring means connecting said rotating means with said upper ring and providing the sole rotational connection therebetween, means for delivering material to be pulverized to said row of grinding elements, and means for withdrawing pulverized material from said housin References Cited by the Examiner UNITED STATES PATENTS 276,145 4/83 Rogers 24ll03 537,947 4/95 Tornaghi 241-103 X 1,040,769 10/12 Sackett 2411O3 2,071,381 2/37 Hardgrove 241-58 2,3 l8,i75 5/43 Lynch 24l-103 J. SPENCER OVERHOLSER, Primary Examiner.

JOHN C. CHRISTIE, Examiner. 

1. A PULVERIZER COMPRISING A HOUSING, A LOWER ROTARY GRINDING RING, MEANS FOR ROTATING SAID LOWER GRINDING RING, A CICULAR ROW OF ROLLING GRINDING ELEMENTS SUPPORTED ON SAID LOWER GRINDING ELEMENTS, MEANS FOR ROTATING SUPPORTED ON SAID GRINDING ELEMENTS, MEANS FOR ROTATING SAID UPPER GRINDING RING IN A DIRECTIN OPPOSIT TO THE DIRECTION OF SAID LOWER GRINDING RING INCLUDING MEANS FOR IMPOSING OF SAID LOWER GRINDING PRESSURE ON SAID GRINDING RINGS AND ELEMENTS, SAID RESILIENT GRINDING PRESSURE MEANS SIMULTANEOUSLY PROVIDING THE SOLE DRIVING CONNECTION BETWEEN SAID ROTATING MEANS AND SAID UPPER GRINDING RING FOR ROTATING SAID UPPER RING, MEANS FOR DELIVERING MATERIAL TO BE PULVERIZED OT SAID ROW OF 